Li+ Insertion/Extraction Properties for TiNb2O7 Single Particle Characterized by a Particle-Current Collector Integrated Microelectrode

Abstract

In this study, we evaluate the electrochemical properties of TiNb2O7 (TNO) single particle using a particle-current collector integrated microelectrode, in which TNO single particle with the size of approximately 10 μm was bonded on the tip of a tungsten microelectrode by platinum deposition using a focused ion beam process unit (FIB). Cyclic voltammogram of TNO single particle showed the reversible redox peaks at around 1.6−1.7 V vs. Li/Li+. Anodic peak current is higher than cathodic one at a fixed scan rate, indicating faster reaction during Li+ extraction (i.e. discharge) than Li+ insertion (i.e. charge) of TNO particle. This tendency was also confirmed in C-rate dependence of charge and discharge capacities. From the results for galvanostatic intermittent titration testing (GITT), we confirmed that at the equilibrium potential vs. Li/Li+ below 1.5 V, apparent chemical diffusion coefficient of Li+ in TNO at Li+ extraction process is much larger than at Li+ insertion process. Furthermore, the capacity retention of TNO single particle tested at current of 10C after 2000 cycles was above 99%, indicating excellent intrinsic stability of TNO single particle for Li+ insertion and extraction reaction.